The idea is an SCP that does not exist in its current state, yet must be contained to the utmost security to prevent existence. If it is not considered a threat or is forgotten, then the SCP materializes to cause mass paranoia and destruction, allowing it to cease to exist, in an infinite cycle that results in multiple repeated XK-CLASS events. Obviously this SCP feeds off of fear and without fear it instigates fear. It’s kind of metaphoric for SCP Foundation censoring unreal information and creating a fear of the nonexistent, and can allude to the purpose of fear being prevention of harm.

Also thinking about making a potential self-insert for the SCP to materialize in or mentally torture or something.

This idea shares a lot of similarities to SCP-2950 and SCP-3930, especially in the execution and story it's trying to tell. I'm not sure how long this idea would survive given that. I think the base concept of the story (the Foundation censoring false information and creating fear of something that doesn't exist) could work, and work better if appended to a different SCP.

Also thinking about making a potential self-insert for the SCP to materialize in or mentally torture or something.

I wouldn't be saying this if you didn't specify that this character was a self-insert, but this might be problematic. At best, it would invite comparisons to SCP-3999. At worst, it would be downvoted to oblivion for the mere inclusion of a SI.

Interesting comparison, but mine is more like, literally nothing in a box. No anomalies in entering the box if you’re still afraid, but the moment you realize there’s nothing to fear, and that “fear itself” is the only thing to fear, the true anomaly that is not within the box takes root from your lack of fear and enters it.

That’s the self insert, the person who is in an interview, speaking with fear.

How would anyone in the Foundation-verse be able to figure this out, though?

Keep in mind that as the author, you know the entire story, but the Foundation needs to have discovered what it knows about the SCP object through observation and experimentation. You'll need to convince your reader that someone with no prior knowledge whatsoever of the anomaly managed to somehow figure out (not magically know!) all the information you've got in the article.

I could make a tale instead, maybe, but most likely it’ll be just another O5 council thing. I’d love to make information regarding the actual SCP hidden across the wiki on mostly dead pages, like an ARG of sorts.

Speaking of which, and slightly off topic, do those exist on here? If you’re unaware, ARGs include Cloverfield and kind of Cicada 3301, and many more of differing difficulty and type.